To provide an antistatic agent which imparts excellent antistatic property to a thermoplastic resin and has ecxellent contamination resistance.

When the antistatic agent comprising a solid neutralized salt (A) obtained by reacting an imidazole compound represented by general formula (1) with a monobasic acid is used in a thermoplastic resin composition, excellent antistatic performance and contamination resistance can be exhibited. In the formula, R1 to R4 are the same or different and each represents H or a 1-10C hydrocarbon group.